Which of these numbers is composite? ${7,\ 37,\ 79,\ 83,\ 87}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 7, 37, 79, and 83 each have only two factors. The factors of 87 are 1, 3, 29, and 87. Thus, 87 is the composite number.